Radiometer apparatus for air disturbance detection

Abstract

A radiometer apparatus is described that is particularly useful for detecting clear air turbulence by sensing infrared radiation. The radiometer includes optics for directing infrared radiation past a chopper, lens and infrared filter assembly to a radiation sensor which produces an analog output signal that is routed through an N-path filter unit and then demodulated and integrated by an averaging integrator to produce temperature indicative differences for determination of the presence of clear air turbulence in the area then being examined by the apparatus, the N-path unit and averaging intergrator providing a high signal to noise ratio. An automatic calibration unit is also provided to provide stability and reliability to the apparatus.

What is claimed is: 
     
       1. A radiometer apparatus with a high signal to noise ratio useful for detecting disturbances in air by measurement of sensed temperature differences, said apparatus comprising: signal developing means for receiving temperature indications relating to disturbances in air and providing an electronic signal output indicative thereof; and   signal processing means including active filtering and integrating means connected with said signal developing means to receive said electronic signal output therefrom and responsive thereto providing an integrated signal with a high signal to noise ratio whereby said signal processing means provides an output signal having a signal level accurately indicative of temperature differences received by said apparatus, said signal processing means including synchronous demodulator means and said active filtering and integrating means including an averaging integrator integrating said output signal from said synchronous demodulator means, with said averaging integrator including signal chopping means operable at a predetermined frequency, switching means connected with said chopping means and receiving said output signal from said synchronous demodulator means, comparison means connected with said chopping means to receive said output signal therefrom, frequency doubling means connected with said signal chopping means, and sample and hold means connected with said comparison means and said frequency doubling means whereby an output signal is provided from said averaging integrator having a high signal to noise ratio.   
     
     
       2. The apparatus of claim 1 wherein said switching means includes a pair of switches, wherein said chopping means supplies a first signal to one of sid switches and a second signal of opposite phase with respect to said first signal to the other of said switches, and wherein said comparison means includes first and second amplifiers each of which has a charging circuit connected therewith and a third amplifier connected with said first and second amplifiers to receive the outputs therefrom. 
     
     
       3. The apparatus of claim 1 wherein said frequency doubling means includes a frequency doubler and a monostable multivibrator. 
     
     
       4. The apparatus of claim 1 wherein said sample and hold means includes a pair of switches having a filter and amplifier connected therebetween, said switches being connected with said frequency doubling means.